Electrical contacts are present in all avionics, military and aerospace equipment environment such as in helicopters, missiles and planes. Such equipment has hundreds or even thousands of electrical connections that must be made between electronic power supplies, sensors, activators, circuit boards, bus wiring, wiring harnesses, to provide the electrical pathways or highways needed to transport electricity in the form of control signals and power. The hardware reliability requirements for operating in an avionics environment are stringent as a failure can have catastrophic consequences. As such, the electrical components and circuitry, as well as the connectors and contacts therein employed to electrically connect these items, must work in a wide range and wide variety of environmental conditions such as mechanical, vibration, wide temperature ranges, humidity and corrosive elements, etc.
For example, military standards (or mil specs) for aircraft avionics equipment require that connector contacts be able to mate and unmate hundreds of times with the respective other contact of the connector without a failure during all anticipated environmental and mechanical conditions. In addition, the contact assemblies must be protected to withstand repeated handling without significant distortion or damage to the interconnecting parts which could lead to a lack of electrical continuity across the connector.
Examples of socket contacts for connectors that are suitable for such uses are illustrated in U.S. Pat. Nos. 6,250,974 and 8,851,940. which include a defined female socket have a cylindrical mating portion or spring defined by cantilever beams or spring fingers. A male contact portion or pin is inserted into the female contact. The spring fingers are formed and bent to define the socket having an inner diameter less than the outer diameter of the pin. The fingers are configured to flex apart to receive the pin and to then bear against the pin under the spring force for a good electrical contact. Such connector contacts must be able to stand up to significant forces in use. One test for such contacts to ensure the fingers have enough elastic flex is referred to as a probe damage test. This test inserts a pin in to the socket at a specified depth and hangs a weight on the pin to deflect the spring to its maximum allowable distance. Then the socket is rotated 360 degrees in order to flex all the springs to their maximum deflection. The socket must be able to pickup a specified weight, therefore ensuring the springs have not deflected beyond the designed intent.
In order to ensure electrical continuity in connectors, some such connectors are commonly formed out of a single piece of material. However, there are drawbacks associated with using the same material to manufacture an entire connector. For example, in manufacturing a socket contact, the front end must have high yield strength to avoid permanent deformation when the socket fingers are deflected (e.g., during mating with a corresponding pin), and the back end must be very ductile to allow permanent deformation without cracking (e.g., during crimping around a conductor). Because materials that have a high yield strength are (generally) not very ductile, and vice versa, it is difficult to manufacture an optimal socket contact out of a single piece of material.
In an effort to overcome this drawback, multi-piece socket contact assemblies have been manufactured. Such a socket contact includes multiple pieces, including a socket body and a spring body. The spring body, during assembly, is press fit onto the socket body. The drawback of such an assembly, however, is that during periods of high vibration, the spring body has a tendency to move in relation to the socket body. While the movement may be minimal (e.g., not resulting in the disassembly of the socket contact), it can be enough to cause fretting, or friction, which can create of a non-conductive barrier. If a non-conductive barrier is formed, the electrical continuity of the conductor is compromised.
To secure the spring body, such contacts often use hoods or sleeves that fit over the spring body and socket body to secure the assembly together. In various designs, the socket body is machined all the way around the socket body to have features which further secure the spring body thereon. Still further, the sleeves of prior art designs must be machined or otherwise formed to have additional features that engage the spring body to secure it on the socket body and/or engage the spring fingers to prevent over flexing or over extension.
As may be appreciated, the additional machining of the socket body and the required formation of additional features in the sleeve, increases the number of steps that are required in forming the multipiece contact. This in turn lowers the throughput in the formation process, and it essentially increases the overall cost of the contact.
Thus, it is desirable to provide a multiple piece electrical contact that addresses various of the drawbacks, can be manufactured more efficiently and cost effectively and still stands up the rigorous environment that is encountered in the use of such contacts.